High frequency oscillator tube



1938. w. DALLENBACH 2,128,231

HIGH FREQUENCY OSCILLATOR TUBE Filed Oct. 11, 1934 2 Sheets-Sheet l 6/70 ibfenf/a/ /n ventor:

WALTER DALLENBAQH wMRQ/MW ATTORNEYS Aug. 30, 1938. w. DALLENBACH HIGHFREQUENCY OSCILLATOR TUBE 2 Sheets-Sheet 2 Filed Oct. 11, 1954 lnventor:WALTER [ALEN EACH QAM Vl/ M ATTORNEYS Patented Aug. 30, 1938 UNITEDSTATES PATENT OFFICE Walter Diillenbach, Berlin-Charlottenburg, Germany,assignor to N. V. Machinerieen-en Apparaten Fabrleken "Meaf,

lands Utrecht, Nether- Applicatlon October 11, 1934, Serial No. 747,948In Germany October 13, 1933 14 Claims.

My invention relates, to an electron tube intended for exciting, i. e.for generating, amplifying or receiving high-frequency, eleotro-magneticoscillations, particularly oscillations having a wave length of lessthan 1 m.

The electron tube consists of a resonator which is excited by a flow ofelectrons. In the province of the high-frequency oscillations,particularly with a wave length of less than 1 m., it is a favourablefeature to design the resonator as free of damping as possible For thepurpose of avoiding stray radiation, which in connection with highfrequencies represents a considerable damping, the resonator isconstructed, in accordance with 5 the present invention, as a hollowspace limited by metallic walls and closed for the exit of strayradiation. In consequence thereof the oscillation of the resonatorattains higher voltage amplitudes than an oscillating circuit with strayradiation. Furthermore, the controlling effect of the resonator upon theexciting flow of electrons will be enhanced. It has thus been renderedpossible, with the aid of the expedient developed in accordance with thepresent invention, to increase in a generator the oscillatory power, inan amplifier the power amplification ratio and in a receiver thereceptive sensitiveness to a considerable degree.

The employment of a hollow space resonator renders it, furthermore,possible to omit the glass vessel otherwise usual with electron tubesand to design the hollow space serving as resonator simultaneously as avacuum vessel. For the purpose of maintaining the flow of electronsexciting the resonator to oscillations, it is essential to impart to theelectrodes, partly formed by the walls of the hollow space serving asresonator, direct voltages. It follows therefrom that it will benecessary to insulate different parts of the w metallic walls of thehollow space from each other and to introduce current conductors intothe closed hollow space. It is advisable to employ for this purposefusions of glass with metal, so that the hollow space serving asresonator consists of two or of a plurality of wall parts, insulatedfrom each other and closely joined, being made, to form a closed andvacuum tight hollow space through the medium of the longitudinalsoldering seams of glass, so to speak.

If the cathode for emitting electrons is disposed outside the hollowspace serving as resonator, it is essential to provide in the wall ofthe hollow space an aperture, through which the flow of electrons entersthe hollow space and excites the oscillation. By means of this aperturewhich may, by way of example, have the form of a grid, the hollow space,serving as resonator, is coupled with the space in which the cathode hasbeen disposed. In many cases it is advisable, that the frequency towhich the 5 electron tube responds, is exclusively determined by one ofthe natural frequencies of the hollow space serving as resonator. Inthis case it is recommended to detune the space enclosing the cathode incontrast to the hollow space serving 10 as resonator, particularly totune it to a higher frequency, so that coupling oscillations between thetwo spaces referred to do not take place.

If this measure is properly observed and if care is taken that generallyno further resonators are 16 connected with the hollow space serving asresonator which might give rise to coupling oscillations, an electrontube will be obtained which is excited only for natural oscillations ofthe hollow space serving as resonator. As generator, 20 therefore, itgenerates a frequency which coincides with that natural frequency of thehollow space serving as resonator which is excited through the medium ofthe flow of electrons; as receiver or amplifier it will likewise respondonly 5 to that natural frequency of the hollow space serving asresonator, which is excited by the flow of electrons.

Figs. 1a and 2a represent two examples of the present invention, inlongitudinal sections 30 through the axis, and Figs. lb and 2b crosssections vertically to the axis of the rotary-symmetrical arrangement.

Fig. 3, finally, is a diagram of condition from which the voltages maybe gathered for which 35 the arrangements in accordance with Fig. 1a andFig. 2a oscillate.

In Figs. 1a and lb A represents a metallic tube of circular crosssection. Coaxially thereto a tube of smaller diameter has been disposed.40 This smaller tube consists of the two tube sections B1 and B2 rigidlyconnected with each other by axial barsof the grid G. The tubes A and B1or B2 are provided at their ends with collars P1, P2 or Q1, Q2 closingup the Lecher system, formed by ABr GB2, at the ends through the mediumof the existing short circuit capacities between the plates P1, Q1, insuch a manner that a penetration of a stray radiation, which wouldexercise a considerable damping effect on the 5 oscillation of theLecher system, through the narrow slits between P1 and Q1 or P2 and Q2,has been rendered impossible.

For the purpose of ensuring to the furthest possible extent an unimpededflow of the high 55 frequency current on the surface of the innerconductor 81 GE, the grid elements are con nected with the tube sectionsB1, B2 parallel to the high frequency current, i. e. parallel to theaxis 0! the arrangement.

In the axis of the arrangement, 1. e. within the high frequencyconductor formed by the parts 31 G Be, a tunsten filament has beenfitted between two substantial cylinders C1, C: as cathode K. Thesecylinders C1, C: are made to support at their ends the plates E1, E2. Inview of the fact that these plates E1, E: are positioned closelyadjacent to the plates Q1, Q1 connected with B1, Ba and also thecylinders C1. C2 leave free only a narrow slit opposite the inside ofthe tubes B1. Ba, it is obvious that the cathode K is situated within ahollow space essentially limited by the grid G and the cylinder facesC1, C2. This hollow space possesses an essentially shorter axial lengththan the Lecher system formed by the conductors A B1, G B: and it is forthis reason detuned to a high frequency in contrast to this Lechersystem. An oscillation within this Lecher system, in which at the pointof the grid G a potential loop is formed, in the vicinity of the platesQ1, Q2, however, potential nodes, will, therefore, not be capable ofexciting the hollow space, within which the cathode K has beenpositioned, to oscillations. For this reason the cathode space has not,in spite of its being coupled with the hollow space A B1 G B1, anydetuning effect upon the hollow space resonator proper.

The hollow space serving as resonator, particularly the tube A, thecollars P1, P1 and the plates E1, E2, simultaneously serve as vacuumvessel for the electron tube. To this end the edges of the plates E1, E1have been fused with the edges of the collars Q1, Q: and P1, P: by meansof glass-seals, so as to be vacuum proof. These glass seals connect theedges of the disk-like members in approximately the same manner aswelded or soldering seams.

For the purpose of exciting oscillations of the Lecher system formed byA 131, G B1, a flow of electrons is utilized passing through the grid Gin the potential loop of the resonator into the hollow space. Inconnection therewith a positive, particularly a high positive directvoltage D is applied to the grid G situated in the potential loop of theresonator relatively to the cathode, while to the tube A a positive ornegative voltage is applied which is below the grid voltage, so thatwithin the space between G and A a brake field is produced. If the tubeA is given a negative voltage relatively to the cathode, this brakefield will produce a reversal of the electrons in the space between Gand A. Flows of electrons of this description will allow of intensivelyexciting an electron tube with hollow space resonator in accordance withFigs. la and lb. For the leading to and from of the oscillation energy,an energy circuit L, for instance in the neighbourhood of a. potentialnode may be coupled in a known manner. One of the conductors of thetransmission line is then passed through the tube A with the aid of theseal 8:. At the free end of the energy circuit any desired loadingresistance or an aerial T may be connected up.

Figs. 2a and 2b represent an arrangement which resembles that of Figs.1a and lb, with the only difference, that instead of the tungstencathode an indirectly heated oxide cathode K1 has been provided andinstead of the round grid bars flat grid bars G1, positioned radially,have been employed, allowing the electrons a convenient passage andembodying a further advantageous effeet, as will be shown in thefollowing.

If in arrangements in accordance with Figs. 1a and 1b the voltage D atthe grid and the voltage at the brake electrode is changed and in thecondition plane in accordance with Fig. 3 those are defined within whichthe tube oscillates, generally two, but frequently also more oscillationranges x or X will be obtained extending along the curves Y or Y. Forvoltages within the crosshatched areas and bordered by X and X the tubesin accordance with Fig. la oscillate with a frequency whose half wavelength very accurately coincides with the distance between the platesQ1, Q2, i. c. with the length of the Lecher system closed at both ends.The curves Y or Y on which a change of the voltage F will exhibit themaximum oscillation amplitude, may be computed in excellent coincidencewith the experiment. The basis for the computation of these curves Y orY is furnished by the conception that electrons emerging from the grid Gand reversing in the space between G and A are caught by the grid aftera single reciprocating path with relatively low speeds. Thepresupposition of such an electron motion is, that the hollow spaceserving as resonator attains alternating amplitudes of its oscillation,at which the electrons are deprived of the kinetic energy, which theypossess when entering the hollow space, during a single reciprocatingpath. These high alternating amplitudes of the oscillation and thesimple electron motion resulting therefrom, i. e. the singlereciprocation path in the field space of the resonator instead of theotherwise occurring multiple electron swingings are the consequence ofthe damping-free design of the resonator, i. e. the consequence ofchoosing as resonator a closed hollow space, from which stray radiationcannot escape.

The excellent coincidence of computation and experiment with regard tothe curves Y or Y along which maximum oscillating amplitudes will showthemselves in connection with a change of the voltage F, proves, thatthe voltages F and D must be so selected, that the electrons require ontheir path in the space between grid and brake electrode a time ofmotion of approximately an integral multiple of the period of theoscillation to be excited, the time of motion in Fig. 3 for theoscillation range X being approximately equal to the period of theoscillation to be excited and for the oscillation range X being aboutdouble that of the period of the oscillation to be excited.

Owing to the fact that the grid, as shown in Figs. 2a and 2b consists offlat bars placed radially, electrons returning from the reversal surfaceto the grid are prevented from reentering the grid cathode space in adisturbing manner. The electrons emanating from the cathode and crossingthe grid G are subject to deviations in a peripheral direction owing tothe fact, that generally they do not enter the resonator accuratelyalong the middle plane between two adjoining grid bars. These deviationscause the electrons returning from the reversal surface not to rushtowards the grid accurately radially, but they cause them to hit thegrid with a peripheral speed component. The structure of the gridcomposed of flat bars mounted radially, thus ensures a safe collectionof the returning electrons.

The employment of a closed hollow space, which does not allow strayradiation to escape, as resonator is independent of the kind of excitingflow of electrons employed. Instead of the tube represented in the Figs.1a, lb, 2a, 2b in brake field connection, a magnetron tube, e. g. with amagnetic field extending parallel to the cathode, could be employed.

It is, of course, possible without any difllculty whatsoever to excitetubes in accordance with Figs. 1a, lb, 2a, 2b by a suitable selection ofthe flow of electrons, particularly by a suitable ad- Justment of thetime of motion in any desired harmonic vibration of the Lecher systeminstead of in the fundamental wave.

In case of a tube intended for transmission the voltages will have to beso adjusted in accordance with Fig. 3, that the condition point issituated in the vicinity of one of the lines Y or Y at which maximumoscillation amplitude will be produced. If a tube in accordance withFigs. 1a to 2a is intended for receiving purposes, the voltages, incontradistinction thereto are to be so selected, that the conditionpoint in Fig. 3 is situated near the edge of one of the oscillationranges X or X. If, moreover, the voltage is so selected as to bepractically zero, particularly only very little negative in contrast tothe cathode, a direct current will be produced over the brake electrodeA in consequence of the excited oscillation through a wave to bereceived. When receiving a modulated wave the demodulation may beeffccted through the medium of this rectifier effect.

The tubes in accordance with the present invention are of particularinterest for the province of the centimeter and the decimeter waves.

I claim:

1. A device for generating, receiving, or amplifying ultra-short wavescomprising an electron tube composed of a cathode, an inner conductorconcentrically mounted about said cathode, and an outer conductorconcentrically mounted about said inner conductor, said inner and outerconductors being separated to form an oscillating I space, said outerconductor consisting of a solid wall metallic tube, said inner conductorconsisting of a solid wall metallic tube formed in two solid wall partsspaced from each other by a grid section, said parts of said innerconductor being separated from each other a distance materially lessthan the axial length of the space between said inner and outerconductors.

2. An evacuated electron tube having two solid wall cylinders formingelectrodes one within the other and spaced to form an oscillatingchamber therebetween, a grid forming part of the inner electrode, acathode within said inner electrode, and means connecting each end ofone electrode to a like end of the other electrode, said means sealingsaid chamber.

3. A tube as in claim 2, said means comprising flanges secured to theends of said electrodes and means sealing said flanges in spacedrelation.

4. A tube as in claim 2, filling means within said inner electrodelimiting the oscillatory system within said inner electrode to a detunedfrequency with respect to the frequency in said chamber.

5. An electron tube, comprising two coaxial hollow metal cylinders,capacitatively short circuited wall portions connected to the ends ofsaid cylinders and in spaced relation to each other, said cylindersbeing spaced away from each other and enclosing therebetween a space,the outer cylinder being a solid wall electrode, the inner cylinderhaving openings therein, the portions of said inner cylinder betweensaid openings being a grid, a cathode mounted coaxially within thehollow cylinder adjacent said openings, members connected with thecathode and forming shortcircuit condensers with the inner hollowcylinder, the inner ends of said members delimiting a space around thecathode which is detuned relative to the resonator space, metal platesconnected to said members, and a glass-metal Joint connecting saidplates and said wall portions vacuum tight.

6. An electron tube, comprising two coaxial hollow metal cylinders,capacitatively short circuited wall portions connected to the ends ofsaid cylinders and in spaced relation to each other, said cylindersbeing spaced away from each other end enclosing therebetween a space,the outer cylinder being a solid wall electrode, the inner cylinderhaving openings therein, the portions of said inner cylinder betweensaid openings being a grid, an indirectly heated oxide cathode mountedcoaxially within the hollow cylinder adjacent said openings, membersconnected with the oathode and forming short-circuit condensers with theinner hollow cylinder, the inner ends of said members delimiting a spacearound the cathode which is detuned relative to the resonator space,metal plates connected to said members, and a glass-metal jointconnecting said plates and said wall portions vacuum tight.

'7. An electron tube, comprising two coaxial hollow metal cylinders,capacitatively short circulted wall portions connected to the ends ofsaid cylinders and in spaced relation to each other, said cylindersbeing spaced away from each other and enclosing therebetween anoscillating space, the outer cylinder being a solid wall electrade, theinner cylinder having a grid portion consisting of rods mounted parallelwith the axis oi the cylinders, a cathode mounted coaxially within thehollow cylinder adjacent said grid, members connected with the cathodeand forming short-circuited condensers with the inner hollow cylinder,said members delimiting a space around the cathode which is detunedrelative to the oscillating space, metal plates connected to saidmembers, and a. glass-metal joint connecting said plates vacuum tightwith the wall portions of the outer cylinder, whereby the outer cylinderand said plates form a vacuum receptacle.

8. An electron tube, comprising two coaxial hollowmetal cylinders,capacitatively short circuited wall portions connected to the ends ofsaid cylinders and in spaced relation to each other, said cylindersbeing spaced away from each other and enclosing therebetween anoscillating space, the outer cylinder being a solid wall electrode, theinner cylinder having a grid portion consisting of radially positionedfiat rods mounted parallel with the axis of the cylinders, a cathodemounted coaxially within the hollow cylinder adjacent said grid, membersconnected with the cathode and forming short-circuit condensers with theinner hollow cylinder, said members delimiting a space around thecathode which is detuned relative to the oscillating space, metal platesconnected to said members, and a glassmetal Joint connecting said platesvacuum tight with the wall portions of the outer cylinder, whereby theouter cylinder and said plates form a vacuum receptacle.

9. An electron tube, comprising two coaxial hollow metal cylinders,capacitatively short circuited wall portions connected to the ends ofsaid cylinders, said cylinders being spaced away from each other andenclosing therebetween a space, the outer cylinder being a solid wallelectrode, the inner cylinder having openings therein, the portionsbetween said openings being a grid, a cathode mounted coaxially withinthe hollow cylinders adjacent said grid, members connected with thecathode and forming shortcircult condensers, with the inner hollowcylinder, metal plates connected to said members, and a glass-metaljoint connecting said plates vacuum tight with the wall portions of theouter cylinder, whereby the outer cylinder and said plates form a vacuumreceptacle.

10. An electron tube, comprising two coaxial hollow metal cylinders,capacitatively short circuited wall portions connected to the ends ofsaid cylinders, said cylinders being spaced away from each other andenclosing therebetween a space, the outer cylinder being a solid wallelectrode, the inner cylinder having openings therein, the portionsbetween said openings being a grid, said grid consisting of a pluralityof radially disposed flat rods mounted in said opening, a cathodemounted coaxially within the hollow cylinders adjacent said grid,members connected with the cathode and forming short-circuit condensers,with the inner hollow cylinder, metal plates connected to said members,and a glass-metal joint connecting said plates vacuum tight with thewall portions of the outer cylinder, whereby the outer cylinder and saidplates form a vacuum receptacle.

11. An apparatus for exciting ultra-high frequency electro-magncticoscillations, comprising an electron tube consisting of two coaxialmetal cylinders spaced away from each other, capacitativelyshort-circuited wall portions mounted in spaced relation to each otheron the ends of said plates and said wall portions vacuum tight.

12. An electron tube comprising, a solid wall electrode, a perforatedelectrode within said first electrode and in spaced relation thereto,condenser plates connected to said electrodes, insulating membersbetween said plates, said plates and said electrodes forming a hollowmember electrically conductive substantially all around at least on itsinner side, a cathode outside said hollow member adjacent the opening ofsaid perforated electrode and leads connected to said electrodes.

13. An electron tube, comprising two coaxial hollow metal cylinders,capacitatively short circuited wall portions connected to the ends ofsaid cylinders and in spaced relation to each other, said cylindersbeing spaced away from each other and enclosing therebetween anoscillating space, the outer cylinder being a solid wall electrode, theinner cylinder having openings therein, the portions of said cylinderbetween said openings being a grid, a cathode mounted coaxially withinthe hollow cylinder adjacent said openings, members connected with thecathode and forming short-circuit condensers with the inner hollowcylinder, the inner ends of said members delimiting a space around thecathode which is tuned to a higher specific frequency than saidoscillating space, metal plates connected to said members, and aglass-metal joint connecting said plates vacuum tight.

14. An electron tube, comprising two coaxial hollow metal cylinders,capacitatively short circuited wall portions connected to the ends ofsaid cylinders, and in spaced relation to each other, said cylindersbeing spaced away from each other and enclosing therebetween anoscillating space, the outer cylinder being a solid wall electrode, theinner cylinder having a grid portion consisting of rods mounted parallelwith the axis of the cylinders, a cathode mounted coaxially within thehollow cylinder adjacent said grid, members connected with the cathodeand forming short-circuit condensers with the inner hollow cylinder,said members delimiting a space around the cathode which is tuned to ahigher specific frequency relative tosaid oscillating space, metalplates connected to said members, and a. glass-metal joint connectingsaid plates vacuum tight with the wall portions of the outer cylinder,whereby the outer cylinder and said plates form a vacuum receptacle.

WALTER nlummacn.

